We will determine the adverse and beneficial health effects of personal UVR exposure and their relationships with climatic and environmental factors that modify the solar UVR spectrum. Date and time stamped personal electronic wristwatch dosimeters will be worn to measure individual UVR exposure over extended periods. Satellite and ground station data will be gathered to establish terrestrial UVR spectral irradiance, cloud, albedo, ozone and aerosol data, at the locations and times of exposure. These dosimeters will be used in field studies in working, water, beach and snow situations in four different countries, including studies with children. The personal dosimetric data combined with diary, ground station and satellite data will show the influence of behaviour, meteorological, environmental and cultural factors on individual UVR exposure doses. The interaction between the personal exposure parameters and the satellite and ground station data will enable the development of a humanized radiative transfer model to assess the future impact of climate change on UVR exposure. This is in contrast to previous models that assume exposure to a given fraction of ambient UVR. We will also determine the effect of UVR exposure on DNA damage and immunity in field conditions. Furthermore, the relationship between UVR exposure and vitamin D status will be determined, thus enabling a direct correlation between important risk and benefit biomarkers. We will also determine the spectral relationship between erythema, UVR-induced immunosuppression and vitamin D status. These studies will determine the value of erythema as a biological weighing function for UVR related health outcomes. Finally, we will perform a systematic review of a wide range of health outcomes from UVR exposure, and integrate our personal UVR exposure and modelling data into existing epidemiological data to estimate measurement error and any effects on current UVR dose response relationships and health outcome.